A mold having a two-mold structure consisting of an upper mold and a lower mold as disclosed in a patent document 1 described below, for example, has been conventionally used as a mold for transferless molding. In a method of resin sealing of an electronic component using the mold of the two-mold structure, a problem must be avoided which is caused by failure of separation of a molded resin from the mold at mold opening. Therefore, a resin is molded with a release film interposed between a melting resin and the mold. In this situation, the release film is attracted through a plurality of holes provided in the mold. With this suction, the release film adheres to a surface of the mold. Therefore, the release film is prevented from moving apart from the surface of the mold and contacting the electronic component. As a result, damaging of the electronic component is prevented.
On the other hand, another method of resin sealing of an electronic component has also been conventionally used, in which method a mold is set to a vacuum state to introduce a resin into a space inside the mold. In this method, the mold is in a clamped state and air inside the mold is evacuated by a suction device. Molding of the resin is performed well with this method because the resin is introduced evenly inside the mold. Therefore, it is desirable to use both of the method using the release film and the method of molding the resin with the mold set to the vacuum state.
When the mold is set to the vacuum state, however, a force of attraction drawing the release film to inside of the mold sometimes becomes larger than a force of attraction of the suction device drawing the release film toward the surface of the mold. A problem of the release film contacting the electronic component inside the mold occurs in this situation. Therefore, when the mold of the two-mold structure is used, it is difficult to use both of the method of resin sealing using the release film and the method of resin sealing in which the resin is introduced into the mold by setting the mold to the vacuum state.
Patent Document 1: Japanese Patent Laying-Open No. 2002-043345 (See Page 15 and FIG. 13)